Ordinarily, in a field or planting site used for agricultural purposes and at a construction site, vehicles and other heavy equipment perform a variety of different tasks which are dependent upon the location on the field or construction site. For example, in a construction area, certain precisely defined regions may be landscaped, others may be contoured or graded, and ditches may be dug or utility lines positioned along certain defined routes. At agricultural sites tile may be laid along selected paths, and grading may be required at particular locations.
Existing systems which are capable of providing position data which could be used by such off-the-road vehicles are insufficiently accurate, require the placement of two or more reference points on or about the site, do not provide the position information to the vehicle itself where it is needed for performing the task, or are prohibitively expensive.
Prior art devices include such devices as the geodimeter which radiates a signal modulated at three or four different frequencies. The signal is reflected from a target and detection circuitry detects phase shifts in the modulated signals in order to determine distance. Such devices utilize electromagnetic energy in both the optical and microwave region of the spectrum. Satellite systems, common radar techniques and inertial position systems, similar to those used in navigational guidance systems, have also been used for position detection.
There is, however, a need for a more simple, less expensive, and more accurate system which can be easily transported to a construction or agricultural site and placed into operation with a minimum of calibration. There is also a need for a system which can conveniently provide the required electronic position coordinate data to each vehicle or other equipment operating on the surface of the site.
Such a device can provide information which can be used, for example, by agricultural equipment for controlling the application of fertilizer, chemical, or seeds at the agricultural site by varying application parameters as a function of position on the site. This would permit site soil surveys to be made, followed by the application of fertilizers, chemicals, or seeds at application rates which are tailored to the specific conditions of each location throughout the field.
For construction purposes such a system could be used for grading in accordance with a predetermined plan or topographic map or, for example, the construction of a ditch, bank, or horizontal flat or inclined space for a parking lot.
The data provided by such a system can be complemented by elevation data available by means of a laser light system currently available from Spectra-Physics of Dayton, Ohio. The Spectra-Physics system scans a laser light beam in a horizontal plane above a field. Vertically elongated detectors upon each vehicle detect the position of incidence of that light beam upon the detector. The position of electronic data representing the relative elevation of the vehicle with respect to the plane of laser light.